enumerate 枚举

内置函数（类）enumerate，Python 官方文档描述如下：

help(enumerate)

Help on class enumerate in module builtins:

class enumerate(object)
 |  enumerate(iterable, start=0)
 |  
 |  Return an enumerate object.
 |  
 |    iterable
 |      an object supporting iteration
 |  
 |  The enumerate object yields pairs containing a count (from start, which
 |  defaults to zero) and a value yielded by the iterable argument.
 |  
 |  enumerate is useful for obtaining an indexed list:
 |      (0, seq[0]), (1, seq[1]), (2, seq[2]), ...
 |  

返回一个可迭代对象（iterable）的枚举对象。枚举对象是一个迭代器，迭代出来是一个个元组，里面包含一个计数值（从 start 开始，默认为 0）和通过迭代 iterable 获得的值。

type(enumerate)

type

e = enumerate({'a':1,'b':2,'c':3})
e

<enumerate at 0x200ccb71240>

next(e)

(0, 'a')

for i in e:
    print(i)

(1, 'b')
(2, 'c')

e = enumerate('abc', 1)
list(e)

[(1, 'a'), (2, 'b'), (3, 'c')]